As a rectifying apparatus of an AC generator for vehicle of this type, there is, for example, a rectifying apparatus described in JP-A-11-220858. Such a rectifying apparatus of an AC generator for vehicle includes a positive-side radiation board with plural (for example, four) positive-side rectifying devices mounted thereon, a negative-side radiation board with plural (for example, four) negative-side rectifying devices mounted thereon, and a terminal board having a wiring member electrically connecting the rectifying devices with a stator winding. For heat sinks, which are radiation boards, an aluminum (hereinafter referred to as Al) material of lightweight and good radiation property is generally used. A metal plate such as an Al plate or copper plate having high thermal conductivity is formed (by die-casting, metal plate working or the like) into a predetermined shape. An output terminal bolt for taking out an output of the generator to outside is pressed into and thereby electrically connected to the positive-side radiation board, and the output terminal bolt is protruding out of an AC generator frame. The output terminal bolt also serves for fixing the rectifying apparatus to the frame. Together with another attachment bolt, it fixes the rectifying apparatus, for example, at two points. Since the AC generator frame functions as a grounding electrode, the positive-side radiation board with the output terminal bolt and the frame are attached in the state of being electrically insulated, while the negative-side radiation board and the frame are directly attached electrically and thermally. The positive-side radiation board and the negative-side radiation board are electrically insulated from each other at the parts where the output terminal bolt and the attachment bolt are inserted, and are superimposed in their axial direction. These radiation boards share the bolts for attachment to the frame. Since the positive-side radiation board with its temperature rising higher than the temperature of the negative-side radiation board is situated more closely to the center of the frame (inner side in the radial direction of the negative-side radiation board), it takes in a cooling stream more efficiently for cooling.
The output terminal bolt is roulette-processed so that its contact area in a fitting range increases, but the radiation boards have smooth surfaces and ordinary hole areas. Roulette-processing normally means formation of protruding and recessed parts on a fitting surface. When the bolt is pressed in, the top of the protruding part of the protruding and recessed parts cuts into the corresponding surface, and as a part of the top shifts to the recessed part and flattened as a whole, the pressed side and the pressing side are tightly integrated.
Generally, the positive-side radiation board is made of an Al material, and the output terminal bolt pressed into the positive-side radiation board and serving for electrical connection is made of a Fe material. Therefore, as a current (output current) flowing through the output terminal bolt that is pressed in is increased, contact thermal resistance of the press-in fitting part increases, and not only the positive-side radiation board but also the negative-side radiation board and an insulating mold on the AC generator frame melt. There is a risk of failure in secure electrical connection.
Moreover, since the Al material has a higher ionization tendency and the output terminal bolt is protruding from the AC generator frame, foreign matter such as water and cooling water easily enters the rectifying apparatus along the output terminal bolt. There is a problem of corrosion and damage of the periphery of the output terminal bolt fitting part.
Furthermore, in attachment to a vehicle, because of a force applied when a wiring is connected to the output terminal bolt, the press-in fitting part on the radiation board may be easily displaced.